# Mass & Conversion Problem

## Homework Statement

A piece of pipe has an outer radius of 4.5cm, an inner radius of 2.8cm and length of 36cm

The density of the pipe is 7.8 g/cm^3

What is the mass of this pipe? Answer is in unites of kg.

## Homework Equations

Density=mass/volume

Mass= (density)(volume)

Volume= mass/density

## The Attempt at a Solution

I subtracted the volume of the hollow inside of the tube from the large radius (2.8+4.5cm) and multiplied that by the density given. Then I converted to kg by dividing by 1000. My answer came up to be appx 40 kg. But I believe I'm wrong.

## Answers and Replies

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I subtracted the volume of the hollow inside of the tube from the large radius (2.8+4.5cm)...
The outer radius is given as 4.5 cm. (No need to add 2.8+4.5.)

Oh yeah thanks.
I thought that i had to add the radii because the diagram on the page made it seem as if the outer radius was that of only the thickness of the pipe.